WASHINGTON — The photo-sharing site Instagram has become wildly popular as a way to trade pictures of pets and friends. But a new trend on the site is making parents cringe: beauty pageants, in which thousands of young girls — many appearing no older than 12 or 13 — submit photographs of themselves for others to judge.

In one case, the mug shots of four girls, middle-school-age or younger, have been pitted against one another. One is all dimples, wearing a hair bow and a big, toothy grin. Another is trying out a pensive, sultry look.

Any of Instagram’s 30 million users can vote on the appearance of the girls in a comments section of the post. Once a girl’s photo receives a certain number of negative remarks, the pageant host, who can remain anonymous, can update it with a big red X or the word “OUT” scratched across her face.

“U.G.L.Y,” wrote one user about a girl, who submitted her photo to one of the pageants identified on Instagram by the keyword “#beautycontest.”

The phenomenon has sparked concern among parents and child-safety advocates who fear that young girls are making themselves vulnerable to adult strangers and participating in often cruel social interactions at a sensitive period of development.

But the contests are the latest example of how technology is pervading the lives of children in ways that parents and teachers struggle to understand or monitor.

“What started out as just a photo-sharing site has become something really pernicious for young girls,” said Rachel Simmons, author of “Odd Girl Out” and a speaker on youth and girls. “What happened was, like most social media experiences, girls co-opted it and imposed their social life on it to compete for attention and in a very exaggerated way.”

It’s difficult to track when the pageants began and who initially set them up. A keyword search of #beautycontest turned up 8,757 posts, while #rateme had 27,593 photo posts. Experts say those two terms represent only a fraction of the activity. Contests are also appearing on other social media sites, including Tumblr and Snapchat — mobile apps that have grown in popularity among youth.

Facebook, which bought Instagram last year, declined to comment. The company has a policy of not allowing anyone under the age of 13 to create an account or share photos on Instagram. But Facebook has been criticized for allowing pre-teens to get around the rule — two years ago, Consumer Reports estimated their presence on Facebook was 7.5 million.

Although users can keep their Instagram accounts private or use pseudonyms, they can expose themselves to the public once they share their photos.

The girls in the beauty contests often did not take care to keep their identities and locations private. Some dressed in shirts embroidered with their schools’ names, others provided a link to their Twitter, Facebook or Tumblr accounts containing information about who they are and where they live.

In December, federal officials strengthened privacy rules for children. But analysts say regulators are not keeping abreast of new technological trends that present fresh questions about the safety of children on the Internet.

“It’s so easy and fun to use, and kids are able to post all the time because they are carrying a smartphone in their pockets all day,” said Stephen Balkam, president of the Family Online Safety Institute.

A recent report by the Pew Research Center’s Internet and American Life Project found four out of 10 teens own smartphones and girls tend to be more active users of the Internet through mobile devices than boys.

“In the realm of 12- to 13-year-old girls, nothing much is voluntary, and the peer pressure is intense to conform and be part of it,” Balkam said.

Hollee Actman Becker, a writer and blogger from Philadelphia, last Saturday discovered her 10-year-old daughter was in an Instagram beauty pageant. Horrified, Becker confronted her daughter and realized the girl didn’t fully grasp the risks of the contest.

Becker said she didn’t know the minimum age for Instagram users is 13. She will let her daughter maintain her account, she said, but has pushed back against contests on the site. She posted a photo of the words “Beauty is Skin Deep” on the palm of her hand.

The photo is beginning to go viral.

13

Minimum age for creating an account or sharing photos on Instagram

7.5 million

Pre-teens thought to have accounts on Facebook, which owns Instagram and has been criticized for allowing kids to get around the age rule

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